subpanel or not

I have a 200 amp 30 space / 40 circuit panel. I am finishing my basement and need more space in the box but everything is full. There are even a couple 15 amp twin breakers in there. Would I be better off with a subpanel or could I squeeze a couple more twins in there? Is changing the main panel to a 40 space / 40 circuit the same as adding some twins to the 30 spacer. Thanks.

 

Subpanel vs. tandem breakers is pretty much of a toss-up. Replacing the main panel would be a lot farther down the list. Personally I'd probably go with the subpanel. It would give you more options, and encourage you to be a bit more generous with the circuits for your basement.

 

Go sub-panel.
I read an article that said that tandem breakers are supposed to be getting the boot in the 2006 NEC.

 

Your 30/40 panel will accept (10) full size poles and (5) tandem breakers on each side of the panel. In other words, you could put (5) tandem breakers (10 circuits) on the bottom 5 bus bar stabs on each side of the panel (total of 20 circuits on tandem breakers. There will be a diagram inside your panel that shows where tandem breakers are allowed. The bus bar stabs will look slightly different on those bottom 5 slots to keep you from installing a tandem breaker where not allowed. If you have full size breakers currently installed in the slots that will accept tandem breakers, you can change those breakers and gain one additional circuit per change. Bottom line is if you count double pole breakers as 2 "handles", your maximum number of "handles" you can have is 40. How many handles do you have now?

I wouldn't worry about tandem breakers getting the "boot" in the future. That probably means they will quit making new panels that will accept tandem breakers. I'm sure tandem breakers will be sold well into the future as replacements or additions to currently exisiting panels. Besides, even if you did run into a problem finding a tandem in the future and needed additional circuitry, you could install a subpanel at that point.

 

As was suggested either way would be fine. Sometimes the choice of a sub comes down putting it in a different location if that helps with the wiring runs.